Plesioth

From Monster Hunter - Wiki on Neoseeker

The Plesioth is part of the Piscine classification of monsters; piscine coming from the Latin word for fish. They comes in two flavors, the normal Plesioth and the Green Plesioth. Being part of the Piscine class, the Plesioth tends to spend most of its time in the water swimming, however one may lure it out of the water by using a multitude of items including sonic bombs and frogs. There is no greater joy, when it comes to fishing, than to pull a Plesioth out of the water.

Once on land, the Plesioth becomes a great annoyance. They especially love using a hip check attack that can hit you, even if you stand on the other side of the attack. However, true to the phrase fish out of water, the Plesioth seems to be knocked over more easily compared to land-based wyverns. A useful tactic, to prevent it from jumping back in the water, is to make note of where the Plesioth runs before it dives in. By placing a shock trap at this spot, you can halt its retreat for at least a few more seconds while also scoring a few free hits.

It is also important to note that the Plesioth can be killed while in the water. If this happens, you will be unable to carve it, so gunner beware.

Another thing, if a Plesioth is in the water, it can use it's water gun attack. It submerges then pops out and spits water.